Solder
Overview
 
Solder (ˈ, ˈ or USA ˈ) is a fusible
Fusible alloy
A fusible alloy is a metal alloy capable of being easily fused, i.e. easily meltable, at relatively low temperatures. Fusible alloys are commonly, but not necessarily, eutectic alloys....

 metal alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

 used to join together metal workpieces and having a melting point below that of the workpiece(s).

Soft solder is what is most often thought of when solder or soldering
Soldering
Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a lower melting point than the workpiece...

 are mentioned and it typically has a melting range of 90 to 450 °C (194 to 842 F). It is commonly used in electronics
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

 and plumbing
Plumbing
Plumbing is the system of pipes and drains installed in a building for the distribution of potable drinking water and the removal of waterborne wastes, and the skilled trade of working with pipes, tubing and plumbing fixtures in such systems. A plumber is someone who installs or repairs piping...

. Alloys that melt between 180 and 190 °C (356 and 374 F) are the most commonly used.
Encyclopedia
Solder (ˈ, ˈ or USA ˈ) is a fusible
Fusible alloy
A fusible alloy is a metal alloy capable of being easily fused, i.e. easily meltable, at relatively low temperatures. Fusible alloys are commonly, but not necessarily, eutectic alloys....

 metal alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

 used to join together metal workpieces and having a melting point below that of the workpiece(s).

Soft solder is what is most often thought of when solder or soldering
Soldering
Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a lower melting point than the workpiece...

 are mentioned and it typically has a melting range of 90 to 450 °C (194 to 842 F). It is commonly used in electronics
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

 and plumbing
Plumbing
Plumbing is the system of pipes and drains installed in a building for the distribution of potable drinking water and the removal of waterborne wastes, and the skilled trade of working with pipes, tubing and plumbing fixtures in such systems. A plumber is someone who installs or repairs piping...

. Alloys that melt between 180 and 190 °C (356 and 374 F) are the most commonly used. By definition, using alloys with melting point above 450 °C is called 'hard soldering', 'silver soldering' or brazing
Brazing
Brazing is a metal-joining process whereby a filler metal is heated above and distributed between two or more close-fitting parts by capillary action. The filler metal is brought slightly above its melting temperature while protected by a suitable atmosphere, usually a flux...

. Soft solder can contain lead and/or flux
Flux (metallurgy)
In metallurgy, a flux , is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time...

 but in many applications lead free solder is used. Perhaps the most common and most familiar form of solder is as a wire or rod, though plumbers often use bars of solder while jewelers often use solder in thin sheets which they cut into snippets. Solder can also come in a paste or as a preformed foil shaped to match the workpiece. The word solder comes from the Middle English
Middle English
Middle English is the stage in the history of the English language during the High and Late Middle Ages, or roughly during the four centuries between the late 11th and the late 15th century....

 word soudur, via Old French
Old French
Old French was the Romance dialect continuum spoken in territories that span roughly the northern half of modern France and parts of modern Belgium and Switzerland from the 9th century to the 14th century...

 solduree and soulder, from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 solidare, meaning "to make solid".

Eutectic alloys melt at a single temperature. Non-eutectic alloys have markedly different solidus
Solidus (chemistry)
In chemistry, materials science, and physics, the solidus is the locus of temperatures below which a given substance is completely solid...

 and liquidus temperature, and within that range they exist as a paste of solid particles in a melt of the lower-melting phase. The pasty state causes some problems during handling; it can however be exploited as it allows molding of the solder during cooling, e.g. for ensuring watertight joint of pipes, resulting in a so called 'wiped joint'.

With the reduction of the size of circuit board features, the size of interconnects shrinks as well. Current densities above 104 A/cm2 are often achieved and electromigration
Electromigration
Electromigration is the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect is important in applications where high direct current densities are used, such as in...

 becomes a concern. At such current densities the Sn63Pb37 solder balls form hillocks on the anode side and voids on the cathode side; the increased content of lead on the anode side suggests lead is the primary migrating species.

Contact with molten solder can cause 'solder embrittlement' of the materials, a type of liquid metal embrittlement
Liquid metal embrittlement
Liquid metal embrittlement is a phenomenon of practical importance, where certain ductile metals experience drastic loss in tensile ductility or undergo brittle fracture when tested in the presence of specific liquid metals. Generally, a tensile stress, either externally applied or internally...

.

Lead solder

Tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...

/lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 solders, also called soft solders, are commercially available with tin concentrations between 5% and 70% by weight. The greater the tin concentration, the greater the solder’s tensile
Tensile strength
Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...

 and shear strength
Shear strength
Shear strength in engineering is a term used to describe the strength of a material or component against the type of yield or structural failure where the material or component fails in shear. A shear load is a force that tends to produce a sliding failure on a material along a plane that is...

s. At the retail level, the two most common alloys are 60/40 Tin/lead (Sn/Pb) which melts at 370 °F or 188 °C and 63/37 Sn/Pb used principally in electrical/electronic work. The 63/37 ratio is notable in that it is a eutectic
Eutectic point
A eutectic system is a mixture of chemical compounds or elements that has a single chemical composition that solidifies at a lower temperature than any other composition. This composition is known as the eutectic composition and the temperature is known as the eutectic temperature...

 mixture, which means:
  1. It has the lowest melting point (183 °C or 361.4 °F) of all the tin/lead alloys; and
  2. The melting point is truly a point — not a range.


In plumbing, a higher proportion of lead was used, commonly 50/50. This had the advantage of making the alloy solidify more slowly, so that it could be wiped over the joint to ensure watertightness, the pipes being physically fitted together before soldering. Although lead water pipes were displaced by copper when the significance of lead poisoning
Lead poisoning
Lead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...

 began to be fully appreciated, lead solder was still used until the 1980s because it was thought that the amount of lead that could leach into water from the solder was negligible from a properly soldered joint. The electrochemical couple of copper and lead promotes corrosion of the lead and tin, however tin is protected by insoluble oxide. Since even small amounts of lead have been found detrimental to health, lead in plumbing solder was replaced by silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

 (food grade applications) or antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...

, with copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 often added, and the proportion of tin was increased (see Lead-free solder.)

The addition of tin improves wetting properties of the alloy; lead itself has poor wetting characteristics. Tin however increases the cost of the solder. High-tin tin-lead alloys have limited use as the workability range can be provided by a cheaper high-lead alloy.

In electronics, printed circuit board
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...

s use solder joints to mount components and create a circuit. For miniaturised PCB joints with surface mount components, solder paste
Solder paste
Solder paste sometimes refers to soldering flux that does not contain solder.Solder paste is used to connect the leads of integrated chip packages to attachment points in the circuit patterns on a printed circuit board...

 has largely replaced solid solder.

Lead-tin solders readily dissolve gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 plating and form brittle intermetallics.

Sn60Pb40 solder oxidizes on the surface with forming complex 4-layer structure: tin(IV) oxide on the surface, below it a layer of tin(II) oxide
Tin(II) oxide
Tin oxide is a compound of tin and oxygen where tin has the oxidation state of +2. There are two forms, a stable blue-black form and a metastable red form.-Preparation and reactions:...

 with finely dispersed lead, below a layer of tin(II) oxide with finely dispersed tin and lead, and the solder alloy itself underneath.

Some alloys, namely of lead and to some degree tin, contain small but significant amounts of radioisotope impurities. The radioisotopes undergoing alpha decay
Alpha decay
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...

 are a concern due to their tendency to cause soft error
Soft error
In electronics and computing, a soft error is an error in a signal or datum which is wrong. Errors may be caused by a defect, usually understood either to be a mistake in design or construction, or a broken component. A soft error is also a signal or datum which is wrong, but is not assumed to...

s. Polonium-210 is especially problematic; lead-210 beta decay
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...

s to bismuth-210 which then beta decays to polonium-210, an intense emitter of alpha particle
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...

s. Uranium-238
Uranium-238
Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239...

 and thorium-232 are other significant contaminants of lead containing alloys.

Lead-free solder

On July 1, 2006 the European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

 Waste Electrical and Electronic Equipment Directive
Waste Electrical and Electronic Equipment Directive
The Waste Electrical and Electronic Equipment Directive is the European Community directive 2002/96/EC on waste electrical and electronic equipment which, together with the RoHS Directive 2002/95/EC, became European Law in February 2003, setting collection, recycling and recovery targets for all...

 (WEEE) and Restriction of Hazardous Substances Directive
Restriction of Hazardous Substances Directive
The Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment 2002/95/EC was adopted in February 2003 by the European Union. The RoHS directive took effect on 1 July 2006, and is required to be enforced and become law in each member state...

 (RoHS) came into effect prohibiting the intentional addition of lead to most consumer electronics produced in the EU. Manufacturers in the U.S. may receive tax benefits by reducing the use of lead-based solder. Lead-free solders in commercial use may contain tin, copper, silver, bismuth
Bismuth
Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...

, indium
Indium
Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...

, zinc, antimony, and traces of other metals. Most lead-free replacements for conventional Sn60/Pb40 and Sn63/Pb37 solder have melting points from 5 to 20 °C higher, though solders with much lower melting points are available.

Drop-in replacements for silkscreen with solder paste soldering operations are available. Minor modification to the solder pots (e.g. titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....

 liners and/or impellers) used in wave-soldering operations may be desired to reduce maintenance costs associated with the increased tin-scavenging effects of high tin solders. Since the properties of lead-free solders are not as thoroughly known, they may therefore be considered less desirable for critical applications, like certain aerospace
Aerospace
Aerospace comprises the atmosphere of Earth and surrounding space. Typically the term is used to refer to the industry that researches, designs, manufactures, operates, and maintains vehicles moving through air and space...

 or medical projects. "Tin whiskers
Whisker (metallurgy)
Metal whiskering is a crystalline metallurgical phenomenon involving the spontaneous growth of tiny, filiform hairs from a metallic surface. The effect is primarily seen on elemental metals but also occurs with alloys....

" were a problem with early electronic solders, and lead was initially added to the alloy in part to eliminate them.

Sn-Ag-Cu (Tin-Silver-Copper) solders are used by two thirds of Japanese manufacturers for reflow and wave soldering
Wave soldering
Wave soldering is a large-scale soldering process by which electronic components are soldered to a printed circuit board to form an electronic assembly. The name is derived from the use of waves of molten solder to attach metal components to the PCB...

, and by about 75% of companies for hand soldering. The widespread use of this popular lead-free solder alloy family is based on the reduced melting point of the Sn-Ag-Cu ternary eutectic behavior (217 ˚C), which is below the Sn-3.5Ag (wt.%) eutectic of 221 °C and the Sn-0.7Cu eutectic of 227 °C (recently revised by P. Snugovsky to Sn-0.9Cu). The ternary eutectic behavior of Sn-Ag-Cu and its application for electronics assembly was discovered (and patented) by a team of researchers from Ames Laboratory
Ames Laboratory
Ames Laboratory is a United States Department of Energy national laboratory located in Ames, Iowa. The Laboratory conducts research into various areas of national concern, including the synthesis and study of new materials, energy resources, high-speed computer design, and environmental cleanup...

, Iowa State University
Iowa State University
Iowa State University of Science and Technology, more commonly known as Iowa State University , is a public land-grant and space-grant research university located in Ames, Iowa, United States. Iowa State has produced astronauts, scientists, and Nobel and Pulitzer Prize winners, along with a host of...

, and from Sandia National Laboratories
Sandia National Laboratories
The Sandia National Laboratories, managed and operated by the Sandia Corporation , are two major United States Department of Energy research and development national laboratories....

-Albuquerque.

Much recent research has focused on selection of 4th element additions to Sn-Ag-Cu to provide compatibility for the reduced cooling rate of solder sphere reflow for assembly of ball grid arrays, e.g., Sn-3.5Ag-0.74Cu-0.21Zn (melting range of 217–220 ˚C) and Sn-3.5Ag-0.85Cu-0.10Mn (melting range of 211–215 ˚C).

Tin-based solders readily dissolve gold, forming brittle intermetallics; for Sn-Pb alloys the critical concentration of gold to embrittle the joint is about 4%. Indium-rich solders (usually indium-lead) are more suitable for soldering thicker gold layer as the dissolution rate of gold in indium is much slower. Tin-rich solders also readily dissolve silver; for soldering silver metallization or surfaces, alloys with addition of silvers are suitable; tin-free alloys are also a choice, though their wettability is poorer. If the soldering time is long enough to form the intermetallics, the tin surface of a joint soldered to gold is very dull.

Flux-core solder


Flux
Flux (metallurgy)
In metallurgy, a flux , is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time...

 is a reducing agent
Reducing agent
A reducing agent is the element or compound in a reduction-oxidation reaction that donates an electron to another species; however, since the reducer loses an electron we say it is "oxidized"...

 designed to help reduce
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 (return oxidized metals to their metallic state) metal oxides at the points of contact to improve the electrical connection and mechanical strength. The two principal types of flux are acid flux, used for metal mending and plumbing, and rosin
Rosin
.Rosin, also called colophony or Greek pitch , is a solid form of resin obtained from pines and some other plants, mostly conifers, produced by heating fresh liquid resin to vaporize the volatile liquid terpene components. It is semi-transparent and varies in color from yellow to black...

 flux, used in electronics, where the corrosiveness of acid flux and vapors released when solder is heated would risk damaging delicate circuitry.

Due to concerns over atmospheric pollution and hazardous waste
Hazardous waste
A hazardous waste is waste that poses substantial or potential threats to public health or the environment. According to the U.S. environmental laws hazardous wastes fall into two major categories: characteristic wastes and listed wastes.Characteristic hazardous wastes are materials that are known...

 disposal, the electronics industry has been gradually shifting from rosin flux to water-soluble flux, which can be removed with deionized water and detergent
Detergent
A detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...

, instead of hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

 solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

s.

In contrast to using traditional bars or coiled wires of all-metal solder and manually applying flux to the parts being joined, some light hand soldering since the mid-20th century has used flux-core solder. This is manufactured as a coiled wire of solder, with one or more continuous bodies of non-acid flux embedded lengthwise inside it. As the solder melts onto the joint, it frees the flux and releases that on it as well.

Hard solder

Hard solders are used for brazing, and melt at higher temperatures. Alloys of copper with either zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

 or silver are the most common.

In silversmithing or jewelry making, special hard solders are used that will pass away assay
Metallurgical assay
A metallurgical assay is a compositional analysis of an ore, metal, or alloy.Some assay methods are suitable for raw materials; others are more appropriate for finished goods. Raw precious metals are assayed by an assay office...

. They contain a high proportion of the metal being soldered and lead is not used in these alloys. These solders vary in hardness, designated as "enameling", "hard", "medium" and "easy". Enameling
Vitreous enamel
Vitreous enamel, also porcelain enamel in U.S. English, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C...

 solder has a high melting point, close to that of the material itself, to prevent the joint desoldering
Desoldering
In electronics, desoldering is the removal of solder and components from a circuit for troubleshooting, for repair purposes, component replacement, and to salvage components...

 during firing in the enameling process. The remaining solder types are used in decreasing order of hardness during the process of making an item, to prevent a previously soldered seam or joint desoldering while additional sites are soldered. Easy solder is also often used for repair work for the same reason. Flux or rouge is also used to prevent joints from desoldering.

Silver solder is also used in manufacturing to join metal parts that cannot be welded
Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...

. The alloys used for these purposes contain a high proportion of silver (up to 40%), and may also contain cadmium
Cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...

.

Solder alloys

Composition Sn Pb Ag Cu Sb Bi In Zn Cd Au oth. M.p.
Melting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...

 °C
S
Solidus (chemistry)
In chemistry, materials science, and physics, the solidus is the locus of temperatures below which a given substance is completely solid...

/L 
Toxic Eutectic  Comments
Pb98Sn2 2 98 316/322 Pb no Non-critical sealing and joining. Body solder
Body solder
Body solder is a type of solder used to smooth the surface of automobile bodies before painting. It has been largely supplanted by Bondo, but many purists and auto customizers continue to use body solder, asserting that it bonds better to sheet metal, feels better, wears better, resists higher...

.
Pb97Sn3 3 97 314/320 Pb no Sn3
Pb96Sn4 4 96 299/310 Pb no Used for coating steel and copper, to provide resistance against mild acids and seawater
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...

.
Pb95Sn5 5 95 308/312 301/314 Pb no Sn5, UNS L54320, ASTM5A, ASTM5B, Indalloy 171. Low cost and good bonding properties. Used for coating steel and copper. Used in both SMT (Surface-mount technology
Surface-mount technology
Surface mount technology is a method for constructing electronic circuits in which the components are mounted directly onto the surface of printed circuit boards . An electronic device so made is called a surface mount device...

) and through-hole electronics. Rapidly dissolves gold and silver, not recommended for those. useful for high-temperature service and step soldering. Remains ductile at very low temperatures, can be used for parts subject to vibration at cryogenic applications. Pb93.5Sn5Ag1.5 provides superior wetting and better strength.
Pb93Sn7 7 93 288/308 Pb no Used for coating steel to provide corrosion resistance, allows subsequent soldering.
Pb90Sn10 10 90 268/302 275/302 Pb no Sn10, UNS L54520, ASTM10B, Indalloy 159. Balls for CBGA components, replaced by SnAg3.9Cu0.6. Low cost and good bonding properties. Rapidly dissolves gold and silver, not recommended for those. Used for fabrication of car radiators
Radiator (engine cooling)
Radiators are used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plant or any similar use of such an engine....

 and fuel tank
Fuel tank
A fuel tank is safe container for flammable fluids. Though any storage tank for fuel may be so called, the term is typically applied to part of an engine system in which the fuel is stored and propelled or released into an engine...

s, for coating and bonding of metals for moderate service temperatures. Body solder. Has low thermal EMF, can be used as an alternative to Cd70 where parasitic thermocouple
Thermocouple
A thermocouple is a device consisting of two different conductors that produce a voltage proportional to a temperature difference between either end of the pair of conductors. Thermocouples are a widely used type of temperature sensor for measurement and control and can also be used to convert a...

 voltage has to be avoided.
Pb88Sn12 12 88 254/296 Pb no Used for fabrication of car radiators and fuel tanks, for coating and bonding of metals for moderate service temperatures. Body solder.
Pb85Sn15 15 85 227/288 Pb no Used for coating tubes and sheets and fabrication of car radiators. Body solder.
Pb80Sn20 20 80 183/280 Pb no Sn20, UNS L54711. Used for coating radiator tubes for joining fins.
Pb75Sn25 25 75 183/266 Pb no Crude solder for construction plumbing works, flame-melted. Used for soldering car engine radiators. Used for machine, dip and hand soldering of plumbing fixtures and fittings. Superior body solder.
Pb70Sn30 30 70 185/255 183/257 Pb no Sn30, UNS L54280, crude solder for construction plumbing works, flame-melted, good for machine and torch soldering. Used for soldering car engine radiators. Used for machine, dip and hand soldering of plumbing fixtures and fittings. Superior body solder.
Pb68Sn32 32 68 253 Pb no "Plumber solder", for construction plumbing works
Pb68Sn30Sb2 30 68 2 185/243 Pb no Pb68
Pb67Sn33 33 67 187–230 Pb no PM 33, crude solder for construction plumbing works, flame-melted, temperature depends on additives
Pb65Sn35 35 65 183/250 Pb no Sn35. Used as a cheaper alternative of Sn60Pb40 for wiping and sweating joints.
Pb60Sn40 40 60 183/238 183/247 Pb no Sn40, UNS L54915,. For soldering of brass
Brass
Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...

 and car radiators. For bulk soldering, and where wider melting point range is desired. For joining cables. For wiping and joining lead pipes. For repairs of radiators and electrical systems.
Pb55Sn45 45 55 183/227 Pb no For soldering radiator cores, roof seams, and for decorative joints.
Sn50Pb50 50 50 183/216 183–212 Pb no Sn50, UNS L55030,. "Ordinary solder", for soldering of brass, electricity meter
Electricity meter
An electricity meter or energy meter is a device that measures the amount of electric energy consumed by a residence, business, or an electrically powered device....

s, gas meter
Gas meter
A gas meter is used to measure the volume of fuel gases such as natural gas and propane. Gas meters are used at residential, commercial, and industrial buildings that consume fuel gas supplied by a gas utility. Gases are more difficult to measure than liquids, as measured volumes are highly...

s, formerly also tin can
Tin can
A tin can, tin , steel can, or a can, is a sealed container for the distribution or storage of goods, composed of thin metal. Many cans require opening by cutting the "end" open; others have removable covers. Cans hold diverse contents: foods, beverages, oil, chemicals, etc."Tin" cans are made...

s. General purpose, for standard tinning and sheetmetal work. Becomes brittle below −150 °C. Low cost and good bonding properties. Rapidly dissolves gold and silver, not recommended for those. For wiping and assembling plumbing joints for non-potable water.
Sn50Pb49Cu1 50 49 1 183/215 Pb no Cu1
Sn50Pb48.5Cu1.5 50 48.5 1.5 183/215 Pb no Savbit, Savbit 1, Sav1. Minimizes dissolution of copper. Originally designed to reduce erosion of the soldering iron tips. About 100 times slower erosion of copper than ordinary tin/lead alloys. Suitable for soldering thin copper platings and very thin copper wires.
Sn60Pb40 60 40 183/190 183/188 Pb near Sn60, ASTM60A, ASTM60B. Common in electronics, most popular leaded alloy for dipping. Low cost and good bonding properties. Used in both SMT and through-hole electronics. Rapidly dissolves gold and silver, not recommended for those. Slightly cheaper than Sn63Pb37, often used instead for cost reasons as the melting point difference is insignificant in practice. On slow cooling gives slightly duller joints than Sn63Pb37.
Sn60Pb38Cu2 60 38 2 183/190 Pb Cu2. Copper content increases hardness of the alloy and inhibits dissolution of soldering iron tips and part leads in molten solder.
Sn60Pb39Cu1 60 39 1 Pb no
Sn62Pb38 62 38 183 Pb near "Tin man's solder"
Sn63Pb37 63 37 182 183 Pb yes Sn63, ASTM63A, ASTM63B. Common in electronics; exceptional tinning and wetting properties, also good for stainless steel. One of most common solders. Low cost and good bonding properties. Used in both SMT and through-hole electronics. Rapidly dissolves gold and silver, not recommended for those. Sn60Pb40 is slightly cheaper and is often used instead for cost reasons, as the melting point difference is insignificant in practice. On slow cooling gives slightly brighter joints than Sn60Pb40.
Sn63Pb37P0.0015–0.04 63 37 P 183 Pb yes Sn63PbP. A special alloy for HASL
HASL
HASL or Hot Air Solder Leveling is a type of finish used on printed circuit boards .- Description :The PCB is typically dipped into a bath of molten solder such that all exposed copper surfaces are covered by solder. Excess solder is removed by scraping the PCB with hot air knives.The HASL process...

 machines. Addition of phosphorus reduces oxidation. Unsuitable for wave soldering as it may form metal foam.
Sn62Pb37Cu1 62 37 1 183 Pb yes Similar to Sn63Pb37. Copper content increases hardness of the alloy and inhibits dissolution of soldering iron tips and part leads in molten solder.
Sn70Pb30 70 30 183/193 Pb no Sn70
Sn90Pb10 90 10 183/213 Pb no formerly used for joints in food industry
Sn95Pb5 95 5 238 Pb no plumbing and heating
Pb92Sn5.5Ag2.5 5.5 92 2.5 286/301 Pb no For higher-temperature applications.
Pb80Sn12Sb8 12 80 8 Pb no Used for soldering iron and steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

Pb80Sn18Ag2 18 80 2 252/260 Pb no Used for soldering iron and steel
Pb79Sn20Sb1 20 79 1 184/270 Pb no Sb1
Pb55Sn43.5Sb1.5 43.5 55 1.5 Pb no General purpose solder. Antimony content improves mechanical properties but causes brittleness when soldering cadmium, zinc, or galvanized metals.
Sn43Pb43Bi14 43 43 14 144/163 Pb no Bi14, Indalloy 97. Good fatigue resistance combined with low melting point. Contains phases of tin and lead-bismuth. Useful for step soldering.
Sn46Pb46Bi8 46 46 8 120/167 Pb no Bi8
Bi52Pb32Sn16 16 32 52 96 Pb yes? Bi52. Good fatigue resistance combined with low melting point. Reasonable shear strength and fatigue properties. Combination with lead-tin solder may dramatically lower melting point and lead to joint failure.
Bi46Sn34Pb20 34 20 46 100/105 Pb no Bi46
Sn62Pb36Ag2 62 36 2 179 Pb yes Sn62. Common in electronics. The strongest tin-lead solder. Appearance identical to Sn60Pb40 or Sn63Pb37. Crystals of Ag3Sn may be seen growing from the solder. Extended heat treatment leads to formation of crystals of binary alloys. Silver content decreases solubility of silver, making the alloy suitable for soldering silver-metallized surfaces, e.g. SMD capacitors and other silver-metallized ceramics. Not recommended for gold. General-purpose.
Sn62.5Pb36Ag2.5 62.5 36 2.5 179 Pb yes
Pb88Sn10Ag2 10 88 2 268/290 267/299 Pb no Sn10, Pb88, Indalloy 228. Silver content reduces solubility of silver coatings in the solder. Not recommended for gold. Forms a eutectic phase, not recommended for operation above 120 °C.
Pb90Sn5Ag5 5 90 5 292 Pb yes
Pb92.5Sn5Ag2.5 5 92.5 2.5 287/296 299/304 Pb no Pb93, Indalloy 151. Similar to Indalloy 165.
Pb93.5Sn5Ag1.5 5 93.5 1.5 296/301 305/306 Pb no Pb94, HMP alloy, HMP. Service temperatures up to 255 °C. Useful for step soldering. Also can be used for extremely low temperatures as it remains ductile down to −200 °C, while solders with more than 20% tin become brittle below −70 °C. Higher strength and better wetting than Pb95Sn5.
Pb95.5Sn2Ag2.5 2 95.5 2.5 299/304 Pb no
In97Ag3 3 97 143 yes Indalloy 290. Wettability and low-temperature malleability of indium, strength improved by addition of silver. Particularly good for cryogenic applications. Used for packaging of photonic devices.
In90Ag10 10 90 143/237 no Indalloy 3. Nearly as wettable and low-temperature malleable as indium. Large plastic range. Can solder silver, fired glass and ceramics.
In75Pb25 25 75 156/165 Pb no Less gold dissolution and more ductile than lead-tin alloys. Used for die attachment, general circuit assembly and packaging closures.
In70Pb30 30 70 160/174 165/175 Pb no In70, Indalloy 204. Suitable for gold, low gold-leaching. Good thermal fatigue properties.
In60Pb40 40 60 174/185 173/181 Pb no In60, Indalloy 205. Low gold-leaching. Good thermal fatigue properties.
In50Pb50 50 50 180/209 178/210 Pb no In50, Indalloy 7. Only one phase. Resoldering with lead-tin solder forms indium-tin and indium-lead phases and leads to formation of cracks between the phases, joint weakening and failure. On gold surfaces gold-indium intermetallics tend to be formed, and the joint then fails in the gold-depleted zone and the gold-rich intermetallic. Less gold dissolution and more ductile than lead-tin alloys. Good thermal fatigue properties.
In50Sn50 50 50 118/125 no Indalloy 1, Cerroseal 35. Fairly well wets glass, quartz and many ceramics. Malleable, can compensate some thermal expansion differences. Low vapor pressure. Used in low temperature physics as a glass-wetting solder.
In70Sn15Pb9.6Cd5.4 15 9.6 70 5.4 125 Pb,Cd Indalloy 13
Pb75In25 75 25 250/264 240/260 Pb no In25, Indalloy 10. Low gold-leaching. Good thermal fatigue properties. Used for die attachment
Die attachment
Die attachment is the step during the integrated circuit packaging phase of semiconductor device fabrication during which a die is mounted and fixed to the package or support structure....

 of e.g. GaAs dies. Used also for general circuit assembly and packaging closures. Less dissolution of gold and more ductile than tin-lead alloy.
Sn70Pb18In12 70 18 12 162
154/167
Pb yes Indalloy 9. General purpose. Good physical properties.
Sn37.5Pb37.5In25 37.5 37.5 25 134/181 Pb no Good wettability. Not recommended for gold.
Pb90In5Ag5 90 5 5 290/310 Pb no
Pb92.5In5Ag2.5 92.5 2.5 5 300/310 Pb no UNS L51510, Indalloy 164. Minimal leaching of gold, good thermal fatigue properties. Reducing atmosphere frequently used..
Pb92.5In5Au2.5 92.5 5 2.5 300/310 Pb no In5
Pb94.5Ag5.5 94.5 5.5 305/364 304/343 Pb no Ag5.5, UNS L50180, Indalloy 229
Pb95Ag5 95 5 305/364 Pb no Indalloy 175
Pb97.5Ag2.5 97.5 2.5 303 304 304/579 Pb yes no Ag2.5, UNS L50132, Indalloy 161. Used during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 to conserve tin. Poor corrosion resistance; joints suffered corrosion in both atmospheric and underground conditions, all had to be replaced with Sn-Pb alloy joints. Torch solder.
Sn97.5Pb1Ag1.5 97.5 1 1.5 305 Pb yes Important for hybrid circuits assembly.
Pb97.5Ag1.5Sn1 1 97.5 1.5 309 Pb yes Ag1.5, ASTM1.5S, Indalloy 165. High melting point, used for commutators, armatures, and initial solder joints where remelting when working on nearby joints is undesirable. Silver content reduces solubility of silver coatings in molten solder. Not recommended for gold. Standard PbAgSn eutectic solder, wide use in semiconductor assembly. Reducing protective atmosphere (e.g. 12% hydrogen) often used. High creep resistance, for use at both elevated and cryogenic temperatures.
Pb54Sn45Ag1 45 54 1 177–210 Pb exceptional strength, silver gives it a bright long-lasting finish; ideal for stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....

Pb96Ag4 96 4 305 Pb high-temperature joints
Pb96Sn2Ag2 2 96 2 252/295 Pb Pb96
Sn61Pb36Ag3 61 36 3 Pb
Sn56Pb39Ag5 56 39 5 Pb
Sn98Ag2 98 2
Sn65Ag25Sb10 65 25 10 233 yes Indalloy 209. Very high tensile strength. For die attachment. Very brittle. Old Motorola die attach solder.
Sn96.5Ag3.0Cu0.5 96.5 3 0.5 217/220 217/218 near SAC305, Indalloy 256, SN97C. Predominantly used in Japan. It is the JEITA
Jeita
Jeita is a Lebanese town located in the Keserwan District in the Mount Lebanon Governorate. The town is about north of Beirut. It is famous for the Jeita Grotto which is a popular tourist attraction, as well as the Nahr al-Kalb, a river that runs from a spring near the grotto emptying into the...

 recommended alloy for wave and reflow soldering
Reflow soldering
Reflow soldering is a process in which a solder paste is used to temporarily attach one or several electrical components to their contact pads, after which the entire assembly is subjected to controlled heat, which melts the solder, permanently connecting the joint...

, with alternatives SnCu for wave and SnAg and SnZnBi for reflow soldering. Usable also for selective soldering and dip soldering. At high temperatures tends to dissolve copper; copper buildup in the bath has detrimental effect (e.g. increased bridging). Copper content must be maintained between 0.4–0.85%, e.g. by refilling the bath with Sn97Ag3 alloy (designated e.g. SN97Ce). Nitrogen atmosphere can be used to reduce losses by dross formation. Dull, surface shows formation of dendritic tin crystals.
Sn95.8Ag3.5Cu0.7 95.8 3.5 0.7 217–218 near SN96C-Ag3.5 A commonly used alloy. Used for wave soldering. Usable also for selective soldering and dip soldering. At high temperatures tends to dissolve copper; copper buildup in the bath has detrimental effect (e.g. increased bridging). Copper content must be maintained between 0.4–0.85%, e.g. by refilling the bath with Sn96.5Ag3.5 alloy (designated e.g. SN96Ce). Nitrogen atmosphere can be used to reduce losses by dross formation. Dull, surface shows formation of dendritic tin crystals.
Sn95.6Ag3.5Cu0.9 95.6 3.5 0.9 217 yes Determined by NIST to be truly eutectic.
Sn95.5Ag3.8Cu0.7 95.5 3.8 0.7 217 almost SN96C. Preferred by the European IDEALS consortium for reflow soldering. Usable also for selective soldering and dip soldering. At high temperatures tends to dissolve copper; copper buildup in the bath has detrimental effect (e.g. increased bridging). Copper content must be maintained between 0.4–0.85%, e.g. by refilling the bath with Sn96.2Ag3.8 alloy (designated e.g. SN96Ce). Nitrogen atmosphere can be used to reduce losses by dross formation. Dull, surface shows formation of dendritic tin crystals.
Sn95.25Ag3.8Cu0.7Sb0.25 95.25 3.8 0.7 0.25 Preferred by the European IDEALS consortium for wave soldering.
Sn95.5Ag3.9Cu0.6 95.5 3.9 0.6 217 yes Indalloy 252. Recommended by the US NEMI consortium for reflow soldering. Used as balls for BGA
Ball grid array
A ball grid array is a type of surface-mount packaging used for integrated circuits.- Description :The BGA is descended from the pin grid array , which is a package with one face covered with pins in a grid pattern. These pins conduct electrical signals from the integrated circuit to the printed...

/CSP
Chip scale package
A chip scale package is a type of integrated circuit chip carrier.Originally, CSP was the acronym for chip-size packaging. Since only a few packages are chip size, the meaning of the acronym was adapted to chip-scale packaging...

 and CBGA components, a replacement for Sn10Pb90. Solder paste for rework of BGA boards. Alloy of choice for general SMT assembly.
Sn95.5Ag4Cu0.5 95.5 4 0.5 217 yes Indalloy 246. Prior-art use makes it patent-free.
Sn96.5Ag3.5 96.5 3.5 221 yes Sn96, Sn96.5, 96S, Indalloy 121. Fine lamellar structure of densely distributed Ag3Sn. Annealing at 125 °C coarsens the structure and softens the solder. Creeps via dislocation climb as a result of lattice diffusion. Used as wire for hand soldering rework; compatible with SnCu0.7, SnAg3Cu0.5, SnAg3.9Cu0.6, and similar alloys. Used as solder spheres for BGA/CSP components. Used for step soldering and die attachment in high power devices. Established history in the industry. Widely used. Strong lead-free joints. Silver content minimizes solubility of silver coatings. Not recommended for gold. Marginal wetting. Good for step soldering. Used for soldering stainless steel as it wets stainless steel better than other soft solders. Silver content does not suppress dissolution of silver metallizations. High tin content allows absorbing significant amount of gold without embrittlement.
Sn96Ag4 96 4 221–229 no ASTM96TS. "Silver-bearing solder". Food service equipment, refrigeration, heating, air conditioning, plumbing. Widely used. Strong lead-free joints. Silver content minimizes solubility of silver coatings. Not recommended for gold.
Sn95Ag5 95 5 221/240 no Sn95. Widely used. Strong lead-free joints. Silver content minimizes solubility of silver coatings. Not recommended for gold.
Sn95Ag4Cu1 95 4 1
Sn 99.99 232 pure Sn99. Good strength, non-dulling. Use in food processing equipment, wire tinning, and alloying. Susceptible to tin pest
Tin pest
Tin pest is an autocatalytic, allotropic transformation of the element tin, which causes deterioration of tin objects at low temperatures. Tin pest has also been called tin disease, tin blight or tin leprosy ....

.
Sn99.3Cu0.7 99.3 0.7 (Ni) 227 yes Indalloy 244, Sn99Cu1. Also designated as Sn99Cu1. Cheap alternative for wave soldering, recommended by the US NEMI consortium. Coarse microstructure with ductile fractures. Sparsely distributed Cu6Sn5. Forms large dendritic β-tin crystals in a network of eutectic microstructure with finely dispersed Cu6Sn5. High melting point unfavorable for SMT use. Low strength, high ductility. Susceptible to tin pest. Addition of small amount of nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

 increases its fluidity; the highest increase occurs at 0.06% Ni. Such alloys are known as nickel modified or nickel stabilized. An example with 0.05% Ni is designated SN100C. The properties degrade with dissolved copper; at above 0.85% the alloy tends to form bridges between part leads. At above 0.9% Cu needles of copper-tin intermetallic precipitate and settle at the bottom of the solder bath. The alloy attacks steel less than the tin-silver-copper alloys, allowing use of stainless steel solder pots. Slower wetting than Sn63Pb37.
Sn99Cu0.7Ag0.3 99 0.3 0.7 217/228 no SCA, SAC, or SnAgCu. Tin-silver-copper
Tin-silver-copper
Tin-silver-copper , is a lead-free alloy commonly used in solder. The tin-silver-copper alloy has been the prevailing alloy system used to replace tin-lead because it is near eutectic, with adequate thermal fatigue properties, strength, and wettability...

 alloy. Relatively low-cost lead-free alloy for simple applications. Can be used for wave, selective and dip soldering. At high temperatures tends to dissolve copper; copper buildup in the bath has detrimental effect (e.g. increased bridging). Copper content must be maintained between 0.4–0.85%, e.g. by refilling the bath with Sn96.2Ag3.8 alloy (designated e.g. SN96Ce). Nitrogen atmosphere can be used to reduce losses by dross formation. Dull, surface shows formation of dendritic tin crystals.
Sn97Cu3 97 3 227/250 232/332 For high-temperature uses. Allows removing insulation from an enameled wire and applying solder coating in a single operation. For radiator repairs, stained glass windows, and potable water plumbing.
Sn97Cu2.75Ag0.25 97 0.25 2.75 228/314 High hardness, creep-resistant. For radiators, stained glass windows, and potable water plumbing. Excellent high-strength solder for radiator repairs. Wide range of patina
Patina
Patina is a tarnish that forms on the surface of bronze and similar metals ; a sheen on wooden furniture produced by age, wear, and polishing; or any such acquired change of a surface through age and exposure...

 and colors.
Zn100 100 419 pure For soldering aluminium. Good wettability of aluminium, relatively good corrosion resistance.
Bi100 100 271 pure Used as a non-superconducting solder in low-temperature physics. Does not wet metals well, forms a mechanically weak joint.
Sn91Zn9 91 9 199 yes Indalloy 201. Cheaper alloy, prone to corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...

 and oxidation. Recommended for soldering aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

. Fair wetting of aluminium, fair corrosion rating. Room temperature tensile strength twice of SnPb37. High drossing. Solder paste has short shelf-life.
Zn95Al5 95 Al5 382 yes For soldering aluminium. Good wetting.
Sn91.8Bi4.8Ag3.4 91.8 3.4 4.8 211/213 no Indalloy 249. Do not use on lead-containing metallizations. U.S. Patent 5,439,639 (ICA Licensed Sandia Patent).
Sn70Zn30 70 30 199/311 no For soldering of aluminium. Good wetting.
Pb63Sn35Sb2 35 63 2 185/243 Pb no Sb2
Pb63Sn34Zn3 34 63 3 170/256 Pb no Poor wetting of aluminium. Poor corrosion rating.
Pb92Cd8 92 8 310? Pb,Cd ? For soldering aluminium. US patent 1,333,666.
Sn48Bi32Pb20 48 20 32 140/160 Pb no For low-temperature soldering of heat-sensitive parts, and for soldering in the vicinity of already soldered joints without their remelting.
Sn89Zn8Bi3 89 3 8 191–198 Prone to corrosion and oxidation due to its zinc content. On copper surfaces forms a brittle Cu-Zn intermetallic layer, reducing the fatigue resistance of the joint; nickel plating of copper inhibits this.
Sn83.6Zn7.6In8.8 83.6 8.8 7.6 181/187 no Indalloy 226. High dross due to zinc. Covered by U.S. Patent #5,242,658.
Sn86.5Zn5.5In4.5Bi3.5 86.5 3.5 4.5 5.5 174/186 no Indalloy 231. Lead-free. Corrosion concerns and high drossing due to zinc content.
Sn86.9In10Ag3.1 86.9 3.1 10 204/205 Indalloy 254. Potential use in flip-chip assembly, no issues with tin-indium eutectic phase.
Sn95Ag3.5Zn1Cu0.5 95 3.5 0.5 1 221L no
Sn95Sb5 95 5 235/240 232/240 no Sb5, ASTM95TA, Indalloy 133. The US plumbing industry standard. It displays good resistance to thermal fatigue and good shear strength. Forms coarse dendrite
Dendrite
Dendrites are the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project...

s of tin-rich solid solution with SbSn intermetallic dispersed between. Very high room-temperature ductility
Ductility
In materials science, ductility is a solid material's ability to deform under tensile stress; this is often characterized by the material's ability to be stretched into a wire. Malleability, a similar property, is a material's ability to deform under compressive stress; this is often characterized...

. Creeps via viscous glide of dislocation
Dislocation
In materials science, a dislocation is a crystallographic defect, or irregularity, within a crystal structure. The presence of dislocations strongly influences many of the properties of materials...

s by pipe diffusion. More creep-resistant than SnAg3.5. Antimony can be toxic. Used for sealing chip packagings, attaching I/O pins to ceramic substrates, and die attachment; a possible lower-temperature replacement of AuSn. High strength and bright finish. Use in air conditioning, refrigeration, some food containers, and high-temperature applications. Good wettability, good long-term shear strength at 100 °C. Suitable for potable water systems. Used for stained glass, plumbing, and radiator repairs.
Sn97Sb3 97 3 232/238 no Indalloy 131
Sn99Sb1 99 1 232/235 no Indalloy 129
Sn99Ag0.3Cu0.7 99 0.3 0.7
Sn96.2Ag2.5Cu0.8Sb0.5 96.2 2.5 0.8 0.5 217–225 217 Ag03A. Patented by AIM alliance
AIM alliance
The AIM alliance was an alliance formed on October 2, 1991, between Apple Inc. , IBM, and Motorola to create a new computing standard based on the PowerPC architecture. The stated goal of the alliance was to challenge the dominant Wintel computing platform with a new computer design and a...

.
Sn88In8.0Ag3.5Bi0.5 88 3.5 0.5 8 197–208 Patented by Matsushita/Panasonic.
Bi57Sn42Ag1 42 1 57 137/139 139/140 Indalloy 282. Addition of silver improves mechanical strength. Established history of use. Good thermal fatigue performance. Patented by Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...

.
Bi58Sn42 42 58 138 yes Bi58, Indalloy 281, Indalloy 138, Cerrothru. Reasonable shear strength and fatigue properties. Combination with lead-tin solder may dramatically lower melting point and lead to joint failure. Low-temperature eutectic solder with high strength. Particularly strong, very brittle. Used extensively in through-hole technology
Through-hole technology
Through-hole technology, also spelled "thru-hole", refers to the mounting scheme used for electronic components that involves the use of leads on the components that are inserted into holes drilled in printed circuit boards and soldered to pads on the opposite side either by manual assembly by...

 assemblies in IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

 mainframe computer
Mainframe computer
Mainframes are powerful computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing.The term originally referred to the...

s where low soldering temperature was required. Can be used as a coating of copper particles to facilitate their bonding under pressure/heat and creating a conductive metallurgical joint. Sensitive to shear rate. Good for electronics. Used in thermoelectric applications. Good thermal fatigue performance. Established history of use. Expands slightly on casting, then undergoes very low further shrinkage or expansion, unlike many other low-temperature alloys which continue changing dimensions for some hours after solidification.
Bi58Pb42 42 58 124/126 Pb Indalloy 67
In80Pb15Ag5 15 5 80 142/149
149/154
Pb no In80, Indalloy 2. Compatible with gold, minimum gold-leaching. Resistant to thermal fatigue. Can be used in step soldering.
Pb60In40 60 40 195/225 Pb no In40, Indalloy 206. Low gold-leaching. Good thermal fatigue properties.
Pb70In30 70 30 245/260 Pb no In30
Sn37.5Pb37.5In26 37.5 37.5 26 134/181 Pb no In26
Sn54Pb26In20 54 26 20 130/154 140/152 Pb no In20, Indalloy 532
Pb81In19 81 19 270/280 260/275 Pb no In19, Indalloy 150. Low gold-leaching. Good thermal fatigue properties.
In52Sn48 48 52 118 yes In52, Indalloy 1E. Suitable for the cases where low-temperature soldering is needed. Can be used for glass sealing. Sharp melting point. Good wettability of glass, quartz, and many ceramics. Good low-temperature malleability, can compensate for different thermal expansion coefficients of joined materials.
Sn52In48 52 48 118/131 no very low tensile strength
Sn58In42 58 42 118/145 no Indalloy 87
Sn51.2Pb30.6Cd18.2 51.2 30.6 18.2 145 Pb,Cd yes Indalloy 181. General-purpose. Maintains creep strength well. Unsuitable for gold.
Sn77.2In20Ag2.8 77.2 2.8 20 175/187 no Indalloy 227. Similar mechanical properties with Sn63Pb37, Sn62Pb36Ag2 and Sn60Pb40, suitable lead-free replacement. Contains eutectic Sn-In phase with melting point at 118 °C, avoid use above 100 °C.
In74Cd26 74 26 123 Cd yes Indalloy 253.
In61.7Bi30.8Cd7.5 30.8 61.7 7.5 62 Cd yes Indalloy 18
Bi47.5Pb25.4Sn12.6Cd9.5In5 12.6 25.4 47.5 5 9.5 57/65 Pb,Cd no Indalloy 140
Bi48Pb25.4Sn12.8Cd9.6In4 12.8 25.4 48 9.6 61/65 Pb,Cd no Indalloy 147
Bi49Pb18Sn15In18 15 18 49 18 58/69 Pb no Indalloy 21
Bi49Pb18Sn12In21 12 18 49 21 58 Pb yes Cerrolow 136. Slightly expands on cooling, later shows slight shrinkage in couple hours afterwards. Used as a solder in low-temperature physics.
Bi50.5Pb27.8Sn12.4Cd9.3 12.4 27.8 50.5 9.3 70/73 Pb,Cd no Indalloy 22
Bi50Pb26.7Sn13.3Cd10 13.3 26.7 50 10 70 Pb,Cd yes Cerrobend. Used in low-temperature physics as a solder.
Bi44.7Pb22.6In19.1Cd5.3Sn8.3 8.3 22.6 44.7 19.1 5.3 47 Cd,Pb yes Indalloy 117, Cerrolow 117. Used as a solder in low-temperature physics.
In60Sn40 40 60 113/122 no
In51.0Bi32.5Sn16.5 16.5 32.5 51 60.5 yes Field's metal
Field's metal
Field's metal, or Field's alloy is a fusible alloy that becomes liquid at approximately . It is a eutectic alloy of bismuth, indium, and tin, with the following percentages by weight: 32.5% Bi, 51% In, 16.5% Sn....

Bi49.5Pb27.3Sn13.1Cd10.1 13.1 27.3 49.5 10.1 70.9 Pb,Cd yes Lipowitz Metal
Bi50.0Pb25.0Sn12.5Cd12.5 12.5 25 50 12.5 71 Pb,Cd yes Wood's metal
Wood's metal
Wood's metal, also known as Lipowitz's alloy or by the commercial names cerrobend, bendalloy, pewtalloy or MCP 158, is a eutectic, fusible alloy with a melting point of approximately . It is a eutectic alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by weight. It...

, mostly used for casting.
Bi50.0Pb31.2Sn18.8 18.8 31.2 50 97 Pb no Newton's metal
Newton's metal
Newton's metal is a fusible alloy with a low melting point. Its composition by weight is 8 parts bismuth, 5 parts lead and 3 parts tin; its melting point is 97 °C....

Bi50Pb28Sn22 22 28 50 109 Pb no Rose's metal
Rose's metal
Rose's metal, Rose metal or Rose's alloy is a fusible alloy with a low melting point.-Properties:Rose's metal consists of 50% bismuth, 25–28% lead and 22–25% tin; its melting point is . The alloy does not contract on cooling.-Uses:...

. It was used to secure cast iron railings and balusters in pockets in stone bases and steps. Does not contract on cooling.
Cd95Ag5 5 95 338/393
340/395
Cd Indalloy 185. melts at 338 °C, flows at 393 °C; for high-temperature applications, for soldering aluminium to itself or to other metals. Braze 053. For medium-strength joints. For low-temperature brazing.
Cd82.5Zn17.5 17.5 82.5 265 Cd For soldering aluminium and die-cast
Die casting
Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process...

 zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

 alloys. Used in cryogenic physics for ataching electrical potential leads to specimens of metals, as this alloy does not become superconductive at liquid helium
Liquid helium
Helium exists in liquid form only at extremely low temperatures. The boiling point and critical point depend on the isotope of the helium; see the table below for values. The density of liquid helium-4 at its boiling point and 1 atmosphere is approximately 0.125 g/mL Helium-4 was first liquefied...

 temperatures.
Zn90Cd10 90 10 265/399 Cd For soldering aluminium. Good wetting.
Zn60Cd40 60 40 265/335 Cd For soldering aluminium. Very good wetting.
Cd70Sn30 29.56 70.44 140/160 Cd no Cd70, thermal-free solder. Produces low thermal EMF joints in copper, does not form parasitic thermocouple
Thermocouple
A thermocouple is a device consisting of two different conductors that produce a voltage proportional to a temperature difference between either end of the pair of conductors. Thermocouples are a widely used type of temperature sensor for measurement and control and can also be used to convert a...

s. Used in low-temperature physics.
Sn50Pb32Cd18 50 32 18 145 Cd,Pb Cd18
Sn40Pb42Cd18 40 42 18 145 Cd,Pb LT145. Low melting temperature allows repairing pewter
Pewter
Pewter is a malleable metal alloy, traditionally 85–99% tin, with the remainder consisting of copper, antimony, bismuth and lead. Copper and antimony act as hardeners while lead is common in the lower grades of pewter, which have a bluish tint. It has a low melting point, around 170–230 °C ,...

 and zinc objects, including die-cast toy
Die-cast toy
The term die-cast toy here refers to any toy or collectible model produced by using the die casting method. The toys are made of metal, with plastic, rubber or glass details. Wholly plastic toys are made by a similar process of injection moulding, but the two are rarely confused...

s.
Zn70Sn30 30 70 199/376 no For soldering aluminium. Excellent wetting. Good strength.
Zn60Sn40 40 60 199/341 no For soldering aluminium. Good wetting.
Zn95Sn5 5 95 382 yes? For soldering aluminium. Excellent wetting.
Sn90Au10 90 10 217 yes Indalloy 238.
Au80Sn20 20 80 280 yes Au80, Indalloy 182, Premabraze 800. Good wetting, high strength, low creep, high corrosion resistance, high thermal conductivity, high surface tension, zero wetting angle. Suitable for step soldering. The original flux-less alloy, does not need flux. Used for die attachment and attachment of metal lids to semiconductor packages, e.g. kovar
Kovar
Kovar is a nickel-cobalt ferrous alloy designed to be compatible with the thermal expansion characteristics of borosilicate glass in order to allow direct mechanical connections over a range of temperatures...

 lids to ceramic chip carrier
Chip carrier
A chip carrier, also known as a chip container or chip package, is a container for a transistor or an integrated circuit. The carrier usually provides metal leads, or "pins", which are sturdy enough to electrically and mechanically connect the fragile chip to a circuit board. This connection may be...

s. Coefficient of expansion matching many common materials. Due to zero wetting angle requires pressure to form a void-free joint. Alloy of choice for joining gold-plated and gold-alloy plated surfaces. As some gold dissolves from the surfaces during soldering and moves the composition to non-eutectic state (1% increase of Au content can increase melting point by 30 °C), subsequent desoldering requires higher temperature. Forms a mixture of two brittle intermetallic phases, AuSn and Au5Sn. Brittle. Proper wetting achieved usually by using nickel surfaces with gold layer on top on both sides of the joint. Comprehensively tested through military standard environmental conditioning. Good long-term electrical performance, history of reliability. Low vapor pressure, suitable for vacuum work. Generally used in applications that require a melting temperature over 150°C. Good ductility. Also classified as a braze.
Au98Si2 98 Si2 370/800 Au98, Indalloy 194. A non-eutectic alloy used for die attachment of silicon dies
Die (integrated circuit)
A die in the context of integrated circuits is a small block of semiconducting material, on which a given functional circuit is fabricated.Typically, integrated circuits are produced in large batches on a single wafer of electronic-grade silicon or other semiconductor through processes such as...

. Ultrasonic assistance is needed to scrub the chip surface so a eutectic (3.1% Si) is reached at reflow.
Au96.8Si3.2 96.8 Si3.2 370 363 yes Au97, Indalloy 184. AuSi3.2 is a eutectic with melting point of 363 °C. AuSi forms a meniscus
Meniscus
The meniscus is the curve in the upper surface of a liquid close to the surface of the container or another object, caused by surface tension. It can be either convex or concave. A convex meniscus occurs when the molecules have a stronger attraction to each other than to the material of the...

 at the edge of the chip, unlike AuSn, as AuSi reacts with the chip surface. Forms a composite material structure of submicron silicon plates in soft gold matrix. Tough, slow crack propagation.
Au87.5Ge12.5 87.5 Ge12.5 361 356 yes Au88, Indalloy 183. Used for die attachment of some chips. The high temperature may be detrimental to the chips and limits reworkability.
Au82In18 18 82 451/485 no Au82, Indalloy 178. High-temperature, extremely hard, very stiff.
In
Indium
Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...

100
99.99 157 pure In99. Used for die attachment of some chips. More suitable for soldering gold, dissolution rate of gold is 17 times slower than in tin-based solders and up to 20% of gold can be tolerated without significant embrittlement. Good performance at cryogenic temperatures. Wets many surfaces incl. quartz, glass, and many ceramics. Deforms indefinitely under load. Does not become brittle even at low temperatures. Used as a solder in low-temperature physics, will bond to aluminium. Can be used for soldering to thin metal films or glass with an ultrasonic soldering iron.


Temperature ranges for solidus and liquidus (the boundaries of the mushy state) are listed as solidus/liquidus.

In the Sn-Pb alloys tensile strength increases with increasing tin content. Indium-tin alloys with high indium content have very low tensile strength.

For soldering semiconductor materials, e.g. die attachment of silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

, germanium
Germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....

 and gallium arsenide, it is important that the solder contains no impurities that could cause doping in wrong direction. For soldering n-type semiconductor
N-type semiconductor
N-type semiconductors are a type of extrinsic semiconductor where the dopant atoms are capable of providing extra conduction electrons to the host material . This creates an excess of negative electron charge carriers....

s, solder may be doped with antimony; indium may be added for soldering p-type semiconductor
P-type semiconductor
A P-type semiconductor is obtained by carrying out a process of doping: that is, adding a certain type of atoms to the semiconductor in order to increase the number of free charge carriers ....

s. Pure tin and pure gold can be used.

Various fusible alloys can be used as solders with very low melting points; examples include Field's metal, Lipowitz's alloy, Wood's metal, and Rose's metal.

Properties

The thermal conductivity of common solders ranges from 32 to 94 W/(m·K) and the density from 9.25 to 15.00 g/cm3.

Solidifying

The solidifying behavior depends on the alloy composition. Pure metals solidify at a sharply defined temperature, forming crystals of one phase. Eutectic alloys also solidify at a single temperature, all components precipitating simultaneously in so-called coupled growth. Non-eutectic compositions on cooling start to first precipitate the non-eutectic phase; dendrites when it is a metal, large crystals when it is an intermetallic compound. Such mixture of solid particles in a molten eutectic is referred to as mushy state. Even a relatively small proportion of solids in the liquid can dramatically lower its fluidity.

The temperature of total solidification is the solidus of the alloy, the temperature at which all components are molten is the liquidus.

The mushy state is desired where a degree of plasticity is beneficial for creating the joint, allowing filling larger gaps or being wiped over the joint (e.g. when soldering pipes). In hand soldering of electronics it may be detrimental as the joint may appear solidified while it is not yet. Premature handling of such joint then disrupts its internal structure and leads to compromised mechanical integrity.

Alloying element roles

Different elements serve different roles in the solder alloy:
  • Antimony
    Antimony
    Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...

     is added to increase strength without affecting wettability. Prevents tin pest. Should be avoided on zinc, cadmium, or galvanized metals as the resulting joint is brittle.
  • Bismuth
    Bismuth
    Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...

     significantly lowers the melting point and improves wettability. In presence of sufficient lead and tin, bismuth forms crystals of Sn16Pb32Bi52 with melting point of only 95 °C, which diffuses along the grain boundaries and may cause a joint failure at relatively low temperatures. A high-power part pre-tinned with an alloy of lead can therefore desolder under load when soldered with a bismuth-containing solder. Such joints are also prone to cracking. Alloys with more than 47% Bi expand upon cooling, which may be used to offset thermal expansion mismatch stresses. Retards growth of tin whiskers. Relatively expensive, limited availability.
  • Copper
    Copper
    Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

     lowers the melting point, improves resistance to thermal cycle fatigue, and improves wetting
    Wetting
    Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. The degree of wetting is determined by a force balance between adhesive and cohesive forces.Wetting is important in the bonding or adherence of...

     properties of the molten solder. It also slows down the rate of dissolution of copper from the board and part leads in the liquid solder. Forms intermetallic compounds. May promote growth of tin whiskers.
  • Indium
    Indium
    Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...

     lowers the melting point and improves ductility. In presence of lead it forms a ternary compound that undergoes phase change at 114 °C. Very high cost (several times of silver), low availability. Easily oxidizes, which causes problems for repairs and reworks, especially when oxide-removing flux cannot be used, e.g. during GaAs die attachment. Indium alloys are used for cryogenic applications, and for soldering gold as gold dissolves in indium much less than in tin. Indium can also solder many nonmetals (e.g. glass, mica, alumina, magnesia, titania, zirconia, porcelain, brick, concrete, and marble). Prone to diffusion into semiconductors and cause undesired doping. At elevated temperatures easily diffuses through metals. Low vapor pressure, suitable for use in vacuum systems. Forms brittle intermetallics with gold; indium-rich solders on thick gold are unreliable. Indium-based solders are prone to corrosion, especially in presence of chloride
    Chloride
    The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...

     ions.
  • Lead
    Lead
    Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

     is inexpensive and has suitable properties. Worse wetting than tin. Toxic, being phased out. Retards growth of tin whiskers, inhibits tin pest. Lowers solubility of copper and other metals in tin.
  • Silver
    Silver
    Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

     provides mechanical strength, but has worse ductility than lead. In absence of lead, it improves resistance to fatigue from thermal cycles. Using SnAg solders with HASL-SnPb-coated leads forms SnPb36Ag2 phase with melting point at 179 °C, which moves to the board-solder interface, solidifies last, and separates from the board. Addition of silver to tin significantly lowers solubility of silver coatings in the tin phase.
  • Tin
    Tin
    Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...

     is the usual main structural metal of the alloy. It has good strength and wetting. On its own it is prone to tin pest and growth of tin whiskers. Readily dissolves silver, gold and to less but still significant extent many other metals, e.g. copper; this is a particular concern for tin-rich alloys with higher melting points and reflow temperatures.
  • Zinc
    Zinc
    Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

     lowers the melting point and is low-cost. However it is highly susceptible to corrosion and oxidation in air, therefore zinc-containing alloys are unsuitable for some purposes, e.g. wave soldering, and zinc-containing solder pastes have shorter shelf life than zinc-free. Can form brittle Cu-Zn intermetallic layers in contact with copper. Readily oxidizes which impairs wetting, requires a suitable flux.

  • Germanium
    Germanium
    Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....

     in tin-based lead-free solders influences formation of oxides; at below 0.002% it increases formation of oxides. Optimal concentration for suppressing oxidation is at 0.005%.

Impurities in solders

Impurities usually enter the solder reservoir by dissolving the metals present in the assemblies being soldered. Dissolving of process equipment is not common as the materials are usually chosen to be insoluble in solder.
  • Aluminium
    Aluminium
    Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

     – little solubility, causes sluggishness of solder and dull gritty appearance due to formation of oxides. Addition of antimony to solders forms Al-Sb intermetallics that are segregated into dross
    Dross
    Dross is a mass of solid impurities floating on a molten metal. It appears usually on the melting of low-melting-point metals or alloys such as tin, lead, zinc or aluminium, or by oxidation of the metal. It can also consist of impurities such as paint leftovers...

    .
  • Antimony
    Antimony
    Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...

     – added intentionally, up to 0.3% improves wetting, larger amounts slowly degrade wetting
  • Arsenic
    Arsenic
    Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

     – forms thin intermetallics with adverse effects on mechanical properties, causes dewetting of brass surfaces
  • Cadmium
    Cadmium
    Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...

     – causes sluggishness of solder, forms oxides and tarnishes
  • Copper
    Copper
    Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

     – most common contaminant, forms needle-shaped intermetallics, causes sluggishness of solders, grittiness of alloys, decreased wetting
  • Gold
    Gold
    Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

     – easily dissolves, forms brittle intermetallics, contamination above 0.5% causes sluggishness and decreases wetting. Lowers melting point of tin-based solders. Higher-tin alloys can absorb more gold without embrittlement.
  • Iron
    Iron
    Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

     – forms intermetallics, causes grittiness, but rate of dissolution is very low; readily dissolves in lead-tin above 427 °C.
  • Nickel
    Nickel
    Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

     – causes grittiness, very little solubility in Sn-Pb
  • Phosphorus
    Phosphorus
    Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

     – forms tin and lead phosphide
    Phosphide
    In chemistry, a phosphide is a compound of phosphorus with a less electronegative element or elements. Binary compounds are formed with the majority of less electronegative elements with the exception of Hg, Pb, Sb, Bi, Te, Po...

    s, causes grittiness and dewetting, present in electroless nickel plating
  • Silver
    Silver
    Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

     – often added intentionally, in high amounts forms intermetallics that cause grittiness and formation of pimples on the solder surface
  • Sulfur
    Sulfur
    Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

     – forms lead and tin sulfide
    Sulfide
    A sulfide is an anion of sulfur in its lowest oxidation state of 2-. Sulfide is also a slightly archaic term for thioethers, a common type of organosulfur compound that are well known for their bad odors.- Properties :...

    s, causes dewetting
  • Zinc
    Zinc
    Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

     – in melt forms excessive dross, in solidified joints rapidly oxidizes on the surface; zinc oxide is insoluble in fluxes, impairing repairability; copper and nickel barrier layers may be needed when soldering brass to prevent nickel migration to the surface

Intermetallics in solders

Many different intermetallic compounds are formed during solidifying of solders and during their reactions with the soldered surfaces. Some of the phases are:

The intermetallics form distinct phases, usually as inclusions in a ductile solid solution matrix, but also can form the matrix itself with metal inclusions or form crystalline matter with different intermetallics. Intermetallics are often hard and brittle. Finely distributed intermetallics in a ductile matrix yield a hard alloy while coarse structure gives a softer alloy. A range of intermetallics often forms between the metal and the solder, with increasing proportion of the metal; e.g. forming a structure of Cu-Cu3Sn-Cu6Sn5-Sn.

Layers of intermetallics can form between the solder and the soldered material. These layers may cause mechanical reliability weakening and brittleness, increased electrical resistance, and/or be susceptible to electromigration and formation of voids. The gold-tin intermetallics layer is responsible for poor mechanical reliability of tin-soldered gold-plated surfaces where the gold plating did not completely dissolve in the solder.

Gold and palladium readily dissolve in solders. Copper and nickel tend to form intermetallic layers during normal soldering profiles. Indium forms intermetallics as well.

Indium-gold intermetallics are brittle and occupy about 4 times more volume than the original gold. Bonding wires are especially susceptible to indium attack. Such intermetallic growth, together with thermal cycling, can lead to failure of the bonding wires.

Copper plated with nickel and gold is often used. The thin gold layer facilitates good solderability of nickel as it protects the nickel from oxidation; the layer has to be thin enough to rapidly and completely dissolve so bare nickel is exposed to the solder.

Lead-tin solder layers on copper leads can form copper-tin intermetallic layers; the solder alloy is then locally depleted of tin and form a lead-rich layer. The Sn-Cu intermetallics then can get exposed to oxidation, resulting in impaired solderability.

Two processes play role in a solder joint formation: interaction between substrate and molten solder, and solid-state growth of intermetallic compounds. The base metal dissolves in the molten solder in amount depending on its solubility in the solder. The active constituent of the solder reacts with the base metal with rate dependent on the solubility of the active constituents in the base metal. The solid-state reactions are more complex; the formation of intermetallics can be inhibited by changing the composition of the base metal or the solder alloy, or by using a suitable barrier layer to inhibit diffusion of the metals.
Tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...

 
Lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 
Indium
Indium
Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...

Copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 
Cu4Sn, Cu6Sn5, Cu3Sn, Cu3Sn8 Cu3In, Cu9In4
Nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

 
Ni3Sn, Ni3Sn2, Ni3Sn4 NiSn3 Ni3In, NiIn Ni2In3, Ni3In7
Iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 
FeSn, FeSn2
Indium
Indium
Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...

 
In3Sn, InSn4 In3Pb
Antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...

 
SbSn
Bismuth
Bismuth
Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...

 
BiPb3
Silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

 
Ag6Sn, Ag3Sn Ag3In, AgIn2
Gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 
Au5Sn, AuSn AuSn2, AuSn4 Au2Pb, AuPb2 AuIn, AuIn2
Palladium
Palladium
Palladium is a chemical element with the chemical symbol Pd and an atomic number of 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired...

 
Pd3Sn, Pd2Sn, Pd3Sn2, PdSn, PdSn2, PdSn4 Pd3In, Pd2In, PdIn Pd2In3
Platinum
Platinum
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...

 
Pt3Sn, Pt2Sn, PtSn, Pt2Sn3, PtSn2, PtSn4 Pt3Pb, PtPb PtPb4 Pt2In3, PtIn2, Pt3In7

  • Cu6Sn5 – common on solder-copper interface, forms preferentially when excess of tin is available; in presence of nickel (Cu,Ni)6Sn5 compound can be formed
  • Cu3Sn – common on solder-copper interface, forms preferentially when excess of copper is available, more thermally stable than Cu6Sn5, often present when higher-temperature soldering occurred
  • Ni3Sn4 – common on solder-nickel interface
  • FeSn2 – very slow formation
  • AuSn4 – β-phase – brittle, forms at excess of tin. Detrimental to properties of tin-based solders to gold-plated layers.
  • AuIn2 – forms on the boundary between gold and indium-lead solder, acts as a barrier against further dissolution of gold

Glass solder

Glass solders are used to join glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

es to other glasses, ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...

s, metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

s, semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...

s, mica
Mica
The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition...

, and other materials, in a process called glass frit bonding
Glass frit bonding
Glass frit bonding, also referred to as glass soldering or seal glass bonding, describes a wafer bonding technique with an intermediate glass layer. It is a widely used encapsulation technology for surface micro-machined structures, i.e. accelerometers or gyroscopes. This technique utilizes low...

. The glass solder has to flow and wet the soldered surfaces well below the temperature where deformation or degradation of either of the joined materials or nearby structures (e.g. metallization layers on chips or ceramic substrates) occurs. The usual temperature of achieving flowing and wetting is between 450 and 550 °C.

Two types of glass solders are used: vitreous, and devitrifying
Devitrification
Devitrification is the opposite of vitrification, i.e., the process of crystallization in a formerly crystal-free glass. The term is derived from the Latin vitreus, meaning glassy and transparent.-Devitrification in glass art:...

. Vitreous solders retain their amorphous structure during remelting, can be reworked repeatedly, and are relatively transparent. Devitrifying solders undergo partial crystallization during solidifying, forming a glass-ceramic
Glass-ceramic
Glass-ceramics are polycrystalline material produced through controlled crystallization of base glass. Glass-ceramic materials share many properties with both glasses and ceramics...

, a composite of glassy and crystalline phases. Devitrifying solders usually create a stronger mechanical bond, but are more temperature-sensitive and the seal is more likely to be leaky; due to their polycrystalline structure they tend to be translucent or opaque. Devitrifying solders are frequently "thermosetting", as their melting temperature after recrystallization becomes significantly higher; this allows soldering the parts together at lower temperature than the subsequent bake-out
Bake-out
Bake-out is a term used in several areas of technology, fabrication, and in building construction, referring to the act of using heat and sometimes a vacuum to release volatile compounds from something as a form of cleaning or processing...

 without remelting the joint afterwards. Devitrifying solders frequently contain up to 25% zinc oxide. In production of cathode ray tube
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

s, devitrifying solders based on PbO-B2O3-ZnO are used.

Very low temperature melting glasses, fluid at 200–400 °C, were developed for sealing applications for electronics. They can consist of binary or ternary mixtures of thallium
Thallium
Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray poor metal resembles tin but discolors when exposed to air. The two chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861 by the newly developed method of flame spectroscopy...

, arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

 and sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

. They are used for sealing of electronic components. Zinc-silicoborate glasses can also be used for passivation of electronics; their coefficient of thermal expansion must match silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

 (or the other semiconductors used) and they must not contain alkaline metals as those would migrate to the semiconductor and cause failures.

The bonding between the glass or ceramics and the glass solder can be either covalent
Covalent bond
A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding....

, or, more often, van der Waals
Van der Waals force
In physical chemistry, the van der Waals force , named after Dutch scientist Johannes Diderik van der Waals, is the sum of the attractive or repulsive forces between molecules other than those due to covalent bonds or to the electrostatic interaction of ions with one another or with neutral...

. The seal can be leak-tight; glass soldering is frequently used in vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...

 technology. Glass solders can be also used as sealant
Sealant
A sealant may be viscous material that has little or no flow characteristics and stay where they are applied or thin and runny so as to allow it to penetrate the substrate by means of capillary reaction...

s; a vitreous enamel coating on iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 lowered its permeability to hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 10 times. Glass solders are frequently used for glass-to-metal seal
Glass-to-metal seal
Glass-to-metal seals are a very important element of the construction of vacuum tubes, electric discharge tubes, incandescent light bulbs, glass encapsulated semiconductor diodes, reed switches, pressure tight glass windows in metal cases, and metal or ceramic packages of electronic...

s and glass-ceramic-to-metal seals.

Glass solders are available as frit
Frit
Frit is a ceramic composition that has been fused in a special fusing oven, quenched to form a glass, and granulated. Frits form an important part of the batches used in compounding enamels and ceramic glazes; the purpose of this pre-fusion is to render any soluble and/or toxic components insoluble...

 powder with grain size below 60 micrometers. They can be mixed with water or alcohol to form a paste for easy application, or with dissolved nitrocellulose
Nitrocellulose
Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton...

 or other suitable binder for adhering to the surfaces until being melted. The eventual binder has to be burned off before melting proceeds, requiring careful firing regime. The solder glass can be also applied from molten state to the area of the future joint during manufacture of the part. Due to their low viscosity in molten state, lead glass
Lead glass
Lead glass is a variety of glass in which lead replaces the calcium content of a typical potash glass. Lead glass contains typically 18–40 weight% lead oxide , while modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO...

es with high PbO
Lead(II) oxide
Lead oxide is the inorganic compound with the formula PbO. Lead oxide occurs in two polymorphs, red, having a tetragonal crystal structure and yellow, having an orthorhombic crystal structure...

 content (often 70–85%) are frequently used. The most common compositions are based on lead borate
Borate
Borates are chemical compounds which contain oxoanions of boron in oxidation state +3. The simplest borate ion, BO33−, has a trigonal planar structure. Other borates are made up of trigonal BO3 or tetrahedral BO4 structural units, sharing oxygen atoms...

s (leaded borate glass or borosilicate glass
Borosilicate glass
Borosilicate glass is a type of glass with the main glass-forming constituents silica and boron oxide. Borosilicate glasses are known for having very low coefficients of thermal expansion , making them resistant to thermal shock, more so than any other common glass...

). Smaller amount of zinc oxide
Zinc oxide
Zinc oxide is an inorganic compound with the formula ZnO. It is a white powder that is insoluble in water. The powder is widely used as an additive into numerous materials and products including plastics, ceramics, glass, cement, rubber , lubricants, paints, ointments, adhesives, sealants,...

 and/or aluminium oxide
Aluminium oxide
Aluminium oxide is an amphoteric oxide with the chemical formula 23. It is commonly referred to as alumina, or corundum in its crystalline form, as well as many other names, reflecting its widespread occurrence in nature and industry...

 can be added for increasing chemical stability. Phosphate glass
Phosphate glass
Phosphate glass is a class of optical glasses composed of metaphosphates of various metals. Instead of SiO2 in silicate glasses, the glass forming substrate is P2O5....

es can be also employed. Zinc oxide, bismuth trioxide
Bismuth trioxide
Bismuth oxide is perhaps the most industrially important compound of bismuth. It is also a common starting point for bismuth chemistry. It is found naturally as the mineral bismite and sphaerobismoite , but it is usually obtained as a by-product of the smelting of copper and lead ores...

, and copper(II) oxide
Copper(II) oxide
Copper oxide or cupric oxide is the higher oxide of copper. As a mineral, it is known as tenorite.-Chemistry:It is a black solid with an ionic structure which melts above 1200 °C with some loss of oxygen...

 can be added for influencing the thermal expansion; unlike the alkali oxides, these lower the softening point without increasing of thermal expansion.

Glass solders are frequently used in electronic packaging
Electronic packaging
Electronic packaging is a major discipline within the field of electronic engineering, and includes a wide variety of technologies. It refers to enclosures and protective features built into the product itself, and not to shipping containers...

. CERDIP packagings are an example. Outgassing of water from the glass solder during encapsulation was a cause of high failure rates of early CERDIP integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

s. Removal of glass-soldered ceramic covers, e.g. for gaining access to the chip for failure analysis
Failure analysis
Failure analysis is the process of collecting and analyzing data to determine the cause of a failure. It is an important discipline in many branches of manufacturing industry, such as the electronics industry, where it is a vital tool used in the development of new products and for the improvement...

 or reverse engineering
Reverse engineering
Reverse engineering is the process of discovering the technological principles of a device, object, or system through analysis of its structure, function, and operation...

, is best done by shearing
Shearing (physics)
Shearing in continuum mechanics refers to the occurrence of a shear strain, which is a deformation of a material substance in which parallel internal surfaces slide past one another. It is induced by a shear stress in the material...

; if this is too risky, the cover is polished away instead.

As the seals can be performed at much lower temperature than with direct joining of glass parts and without use of flame (using a temperature-controlled kiln
Kiln
A kiln is a thermally insulated chamber, or oven, in which a controlled temperature regime is produced. Uses include the hardening, burning or drying of materials...

 or oven), glass solders are useful in applications like subminiature vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...

s or for joining mica windows to vacuum tubes and instruments (e.g. Geiger tube). Thermal expansion coefficient has to be matched to the materials being joined and often is chosen to lay between the coefficients of expansion of the materials. In case of having to compromise, subjecting the joint to compression stresses is more desirable than to tensile stresses. The expansion matching is not critical in applications where thin layers are used on small areas, e.g. fireable ink
Ink
Ink is a liquid or paste that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush, or quill...

s, or where the joint will be subjected to a permanent compression (e.g. by an external steel shell) offsetting the thermally introduced tensile stresses.

Glass solder can be used as an intermediate layer when joining materials (glasses, ceramics) with significantly different coefficient of thermal expansion; such materials cannot be directly joined by diffusion welding
Diffusion welding
Diffusion welding is a solid state welding process by which two metals can be bonded together. Diffusion involves the migration of atoms across the joint, due to concentration gradients. The two materials are pressed together at an elevated temperature usually between 50 and 70% of the melting...

. Evacuated glazing window
Window
A window is a transparent or translucent opening in a wall or door that allows the passage of light and, if not closed or sealed, air and sound. Windows are usually glazed or covered in some other transparent or translucent material like float glass. Windows are held in place by frames, which...

s are made of glass panels soldered together.

A glass solder is used for e.g. joining together parts of cathode ray tubes and plasma display
Plasma display
A plasma display panel is a type of flat panel display common to large TV displays or larger. They are called "plasma" displays because the technology utilizes small cells containing electrically charged ionized gases, or what are in essence chambers more commonly known as fluorescent...

 panels. Newer compositions lowered the usage temperature from 450 to 390 °C by reducing the lead(II) oxide content down from 70%, increasing the zinc oxide content, adding titanium dioxide
Titanium dioxide
Titanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula . When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891. Generally it comes in two different forms, rutile and anatase. It has a wide range of...

 and bismuth(III) oxide and some other components. The high thermal expansion
Thermal expansion
Thermal expansion is the tendency of matter to change in volume in response to a change in temperature.When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation. Materials which contract with increasing temperature are rare; this effect is...

 of such glass can be reduced by a suitable ceramic filler. Lead-free solder glasses with soldering temperature of 450 °C were also developed.

Phosphate glasses with low melting temperature were developed. One of such compositions is phosphorus pentoxide
Phosphorus pentoxide
Phosphorus pentoxide is a chemical compound with molecular formula P4O10 . This white crystalline solid is the anhydride of phosphoric acid. It is a powerful desiccant.-Structure:...

, lead(II) oxide, and zinc oxide, with addition of lithium and some other oxides.

Conductive glass solders can be also prepared.

Preform

A preform is a specially designed shape of solder adjusted to the application where it is used. Although there are many methods that are used to manufacture the solder preform, stamping is probably the most common method. The solder preform can be manufactured including the solder flux needed for the soldering process. This can be an internal flux, inside the solder preform, or external, where the solder preform is coated.

External links

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